Nanocomposite magnetic materials for magnetic devices and systems

ABSTRACT

Nanocomposite magnetic materials, methods of manufacturing nanocomposite magnetic materials, and magnetic devices and systems using these nanocomposite magnetic materials are described. A nanocomposite magnetic material can be formed using an electro-infiltration process where nanomaterials (synthesized with tailored size, shape, magnetic properties, and surface chemistries) are infiltrated by electroplated magnetic metals after consolidating the nanomaterials into porous microstructures on planar substrates. The nanomaterials may be considered the inclusion phase, and the magnetic metals may be considered the matrix phase of the multi-phase nanocomposite.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. applicationSer. No. 14/904,887, filed Jan. 13, 2016, which is a national stageapplication of International Application No. PCT/US2014/048142, filedJul. 25, 2014, which claims the benefit of U.S. Provisional ApplicationSer. No. 61/858,987, filed Jul. 26, 2013, the disclosures of each ofwhich are hereby incorporated by reference in their entirety, includingall figures, tables and drawings.

BACKGROUND

Magnetic materials are used in many different compact devices andsystems. The magnetic materials of interest for these systems exhibit aferromagnetic or ferrimagnetic response, and more specifically, a largemagnetization in response to an applied magnetic field. These magneticmaterials are generally sub-categorized into either soft magneticmaterials, which have a lower coercivity (generally <1 kA/m), or hardmagnetic materials, which have a higher coercivity (generally >10 kA/m).

Soft magnetic materials are used in a wide array of electronic devices.For example, power electronic circuits for power conversion andregulation often include magnetic passives such as inductors andtransformers, which use soft magnetic materials in the inductor andtransformer cores. Furthermore RF/microwave radio circuits for wirelessconnectivity utilize inductors and transformers, as well as phaseshifters, circulators, and isolators, which also employ soft magneticmaterials. These magnetic passives tend to be the largest, heaviest,and/or most inefficient system components of the circuits to which theyform a part.

Limitations of magnetic materials used in soft magnetic cores forforming magnetic passives include magnetic saturation and core loss,particularly at high operational frequencies (1 MHz-10 GHz). Inaddition, core loss may be dominated by eddy current losses.

Hard magnetic materials (permanent magnet behavior) are also used in awide variety of devices. For example, hard magnets supply the magneticfields for electrodynamic or magnetic transduction in actuators,energy-converters, motors, and generators. Hard magnets are also used toprovide bias fields or a fixed magnetic moment for magnetic fieldsensors, proximity sensors, biomedical devices, and other devices wherea stable magnetic field is required. Hard magnets are also used to formmagnetic latches.

Limitations of magnetic materials used in hard micromagnets includecoercivity, remanence, maximum energy product, chemical stability (e.g.propensity for oxidation or corrosion), and temperature sensitivity.

One challenge in forming small-scale magnetic devices and systems isrelated to the dimensional requirements of the necessary magneticmaterials. Magnetic structures with critical dimensions ranging fromones of micrometers up to hundreds of micrometers are desired, but thesestructural dimensions fall in a “technology gap” between thin-filmprocessing and bulk manufacturing.

That is, bottom-up thin-film deposition processes do not easily yieldthick enough magnetic layers (e.g., on the order of micrometers).Conversely, top-down machining of fine-scale structures from bulkmaterials is challenging, and assembly of these structures intofunctional devices requires extensive packaging overhead, which increasesize and cost. Thus, it is difficult to achieve thick magnetic materialswith good magnetic properties in a highly manufacturable process, sinceit is challenging to achieve both manufacturability and performance atthe same time.

Because of this technology gap, magnetic materials remain notoriouslydifficult to integrate into planar substrate manufacturing processessuch as wafer-level electronics manufacturing or printed-circuit-boardmanufacturing. Hence, these wafer-level and board-level integrationchallenges inhibit the use of magnetic materials in the formation ofsmall-scale magnetic devices and systems.

Another challenge in manufacturing small-scale magnetic devices andsystems in a manner that enables high-throughput as well ascompatibility and integration with existing manufacturing platforms isthat the material properties of a magnetic material are strongly coupledwith the material synthesis/deposition process. Changing the thicknessof a deposited magnetic film can alter the resulting material propertiesdue to, for example, stoichiometry differences, stress, and shapeanisotropy.

BRIEF SUMMARY

nanocomposite magnetic materials, methods of manufacturing nanocompositemagnetic materials, and magnetic devices and systems using thesenanocomposite magnetic materials are described.

One aspect of the present invention is directed toward nanocompositemagnetic materials that exhibit properties suitable for use insmall-scale devices and systems. A nanocomposite magnetic materialstructure of certain embodiments can be of dimensions of 1 μm to 1 mm.The nanocomposite magnetic material can include a matrix phase and aninclusion phase. The matrix phase acts as a binder for the inclusionphase and can include magnetic material. The inclusion phase can includenanomaterials such as magnetic metal oxides, magnetic metal alloys,magnetic metal alloys with oxide shells, ceramics, or polymers. Theinclusion phase nanomaterials may have a variety of sizes, shapes,surface coatings, and magnetic properties.

An electro-infiltration process can be performed to form thenanocomposite magnetic materials on planar substrates. Theelectro-infiltration process described herein can form dimensionallycontrolled sub-millimeter magnetic nanocomposite structures in ascalable, batch-fabrication manner. The magnetic structures can beemployed to form magnetic devices (e.g., magnetic passives, magneticactuators) and magnetic systems power conversion systems, magneticsensor systems, biomedical devices).

Another aspect of the present invention is directed toward theelectro-infiltration process to form the nanocomposite magneticmaterials. In certain implementations, nanomaterials are firstsynthesized with tailored size, shape, magnetic properties, and surfacechemistries. In some cases, monodisperse particles can be formed. Then,directed assembly methods, conducted at low temperatures, can be used toconsolidate the nanomaterials (i.e., the inclusion phase) into porousmicrostructures on planar substrates. These porous structures can thenbe infiltrated with electroplated magnetic metals (i.e. the matrixphase) to form multi-phase nanocomposite magnetic materials withmagnetic properties.

A further aspect of the present invention is directed to a magneticdevice formed of the nanocomposite magnetic materials. The magneticdevice may be, as an example, a transformer, an inductor, a radiofrequency (RF) device, a microwave device, an actuator, a motor, agenerator, or an energy converter.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C illustrate a method of manufacturing a nanocompositemagnetic material according to an implementation of the invention.

FIGS. 2A-2D illustrate nanocomposite magnetic materials according tosome implementations of the invention. FIG. 2A shows inclusion phasenanoparticles in a matrix;

FIG. 2B shows inclusion phase core/shell nanoparticles in a matrix; FIG.2C shows nanowires in a matrix; and FIG. 2D shows aligned nanowires in amatrix.

FIG. 3 is a schematic illustrating the strong dependence of coercivityon particle size.

FIGS. 4A-4E illustrate packing arrangements of particles that may beimplemented based on particle size and shape.

FIGS. 5A-5C show example air-core inductor (FIG. 5A), transformer (FIG.5B), and magnetically tunable phase shifter (FIG. 5C) configurationsthat may be fabricated on planar substrates and formed of thenanocomposite materials of certain embodiments of the invention.

FIGS. 6A and 6B respectively show images of the surface of a samplebefore and after the electro-infiltration step

FIG. 7 is a scanning electron microscopy (SEM) image of a cleaved samplecross-section of a nanocomposite showing the progression of theelectroplating growth front moving up through the nanoparticles.

FIG. 8 is a transmission electron microscopy (TEM) image of a samplecross-section showing a dense composite with intimate phase boundaries(inset).

FIG. 9 shows a plot of hysteresis loops of electroplated Fe—Co layer,γ-Fe₂O₃ nanoparticle layer, and γ-Fe₂O₃/Fe—Co nanocomposite layer.

FIGS. 10A and 10B show schematic representations of a γ-Fe₂O₃/Fe—Conanocomposite layer and a γ-Fe₂O₃/Fe—Co double layer, respectively.

FIG. 11 shows a comparison of normalized hysteresis loops of theγ-Fe₂O₃/Fe—Co nanocomposite and γ-Fe₂O₃/Fe—Co double layer.

FIGS. 12A and 12B show plots of the complex relative permeability forthe γ-Fe₂O₃ nanoparticle layer, γ-Fe₂O₃/Fe—Co nanocomposite layer andFe—Co layer, where FIG. 12A shows the real part ν′_(r)(ω) and FIG. 12Bshows the imaginary part μ″_(r)(ω).

FIGS. 13A-13C show the X-ray diffraction pattern (FIG. 13A), TEMmicrograph (FIG. 13B), and particle size distribution (FIG. 13C) forNi_(0.5)Zn_(0.5)Fe₂O₄ particles prepared via aqueous co-precipitation,according to an example implementation.

FIG. 14 illustrates surface functionalization for Ni_(0.5)Zn_(0.5)Fe₂O₄particles prepared via aqueous co-precipitation, according to theexample implementation.

DETAILED DESCRIPTION

Nanocomposite magnetic materials, methods of manufacturing nanocompositemagnetic materials, and magnetic devices and systems using thesenanocomposite magnetic materials are described.

According to certain embodiments, the nanocomposite magnetic materialmay be formed of a nanostructured inclusion phase and a matrix phase.The inclusion phase refers to the nanomaterials (i.e., “nanoparticles,”“nanowires,” “nanorods”) and/or impurities forming the nanocompositemagnetic material. A nanomaterial is a material that has a structuraldimension of <100 nm in at least one dimension. The matrix phase refersto the binding that creates a high-volume-density, high-magnetic-momentnanocomposite magnetic material. Thus, “matrix phase” and “binder” maybe used interchangeably herein.

An electro-infiltration process is performed to form the nanocompositemagnetic materials on planar substrates. The electro-infiltrationprocess can form dimensionally controlled sub-millimeter magneticnanocomposite structures in a scalable, batch-fabrication manner. Themagnetic structures can be employed to form magnetic devices (e.g.,magnetic passives, magnetic actuators) and magnetic systems (e.g. powerconversion systems, magnetic sensor systems, biomedical devices).

FIGS. 1A-1C illustrate a method of manufacturing a nanocompositematerial according to an implementation of the invention. Referring toFIG. 1A, a nanomaterial inclusion phase can be assembled (S101). In somecases, the nanomaterial inclusion phase may be formed of multipleinclusion phases (or types of nanomaterials).

The assembly of nanomaterials 105 can be directed into structurallydefined molds 110, forming porous microstructures (“particleconsolidates”) 115 on a planar substrate 120. The planar substrate 120may be a silicon wafer, printed circuit board (PCB), lead-frame, orother circuit or package substrate. The structurally defined molds 110may be formed of photoresist, etched into a layer of the substrate 120,or fabricated by any other suitable technique.

In certain implementations, the molds 110 may have plan view dimensionsof any of the following values, about any of the following values, atleast any of the following values, at most any of the following values,or within any range having any of the following values as endpoints,though embodiments are not limited thereto: 100 nm, 250 nm, 500 nm, 1μm, 2.5 μm, 5 μm, 25 μm, 50 μm, 100 μm, 250 μm, 500 μm, 1 mm, 2.5 mm, 5mm, 10 mm, 25 mm, 50 mm, 100 mm.

In some implementations, the molds may be omitted and the nanocompositematerial formed directly on a substrate or structure.

The nanomaterials 105 may be directed into the molds 110 (or otherstructure when molds are not used), for example, via doctor Wading,mechanical compaction, direct-write (e.g. inkjet printing) technology,evaporative consolidation, electrophoretic deposition, ormagnetophoretic deposition.

In electrophoretic deposition, colloidal particles in liquid mediummigrate under the influence of an electric field and then deposit on thesurface. An electric bias can be applied to a conductive seed layer onthe substrate 120. In the presence of the electric bias, the particlescan deposit on the exposed surfaces of the substrate 120. An ac electricfield can be used to enact selective spatial deposition and to provideorientation of anisotropic particles such as ferrite nanowires. Theelectrophoretic deposition may be a two-step process where chargednanoparticles are placed in suspension and through e action of anelectric field move toward and deposit on an oppositely charged surface.

Magnetophoretic deposition uses magnetic field gradients to attract themagnetic particles into the molds. In one approach, external magnets maybe placed behind the substrate 120 and lateral agitation of thesemagnets can help confine the particles to the molds. If the particlesremain stable in solution even in the presence of an external magneticfield, as is the case for ferrofluids, the ionic strength and pH of thesolution can be adjusted to destabilize the particles leading them toagglomerate and settle. The external magnets can also be used provide auniform magnetic field to align anisotropic particles such as ferritenanowires to enable anisotropic composites. “Particles” may be of anyshape and are not necessarily spherical.

The consolidated particles need to be very volumetrically dense. Forexample the target densities may be in the range of 25-50%, so thatthere is sufficient porosity for the electro-infiltration process tooccur.

The inclusion phase of the nanocomposite magnetic material can includenanomaterials such as magnetic metal oxide, soft magnetic or hardmagnetic metal alloy, magnetic metal alloy with an oxide shell,ceramics, or polymers. The inclusion phase nanomaterials may have avariety of sizes, shapes, surface coatings, and magnetic properties.These inclusion phase materials form a nanogranular dielectric phasethat disrupts the formation of eddy currents, while also providingadditional magnetic moment. In some implementations, the inclusion phasemay be magnetostrictive.

For implementations using magnetic metal oxide for the nanomaterials,the nanomaterials may include Ni_(1-x)Zn_(x)Fe₂O₄ (where 0≦x≦1) orMn_(1-x)Zn_(x)Fe₂O₄ (where 0≦x≦1). For implementations using magneticmetal alloy for the nanomaterials, soft magnetic material such as Ni,Fe, Co, NiFe, CoFe, or other transition metal magnetic alloys; or hardmagnetic material such as CoNi, CoPt, FePt, NdFeB, SmCo, or othertransition metal or rare-earth-based magnetic alloy, may be included.For implementations using magnetic metal alloy with an oxide shell, themetal alloy can be formed with an oxide surface layer in air or viachemical synthesis.

Referring to FIG. 1B, a magnetic metal matrix 125 can be electroplatedup (S102) from the substrate 120, filling in the void spaces of theporous microstructure 115. Electroplating can use an electric current toreduce metal ions from a solution (such as an electrolyte) and deposit adense metal coating on a conducting surface. For surfaces that are nothighly conducting (such as an oxide surface or a silicon surface), aseed layer of a metal can be sputtered or evaporated onto the surface.In some cases, the electroplating may be steady electroplating, forexample constant current electroplating (galvanostatic) or constantvoltage electroplating (potentiostatic). In other cases, theelectroplating may be pulse or pulse-reverse plating. Alternatively,electroless plating techniques may be used to infiltrate the porousmicrostructure. This step (S102) can be referred to aselectro-infiltrating a metal matrix. That is, “electro-infiltrating”refers to a process by which metal is electroplated up through a porousmicrostructure. Both electroplating and electro-less plating arecontemplated as being processes available for “electro-infiltrating” themetal matrix up through a porous microstructure.

The magnetic metal matrix 125 (matrix phase) may be selected to providea high-saturation, low-coercivity magnetic property for thenanocomposite. For example, the matrix phase, or binder, may be magneticand include soft magnetic material such as Ni, Fe, Co, NiFe, CoFe, orother transition metal magnetic alloys.

The magnetic metal matrix 125 (matrix phase) may be selected to providea high-saturation, high-coercivity or hard magnetic property for thenanocomposite. For example, the matrix phase, or binder, may be magneticand include hard magnetic material such as CoNi, CoPt, FePt, NdFeB,SmCo, or other transition metal or rare-earth-based magnetic alloy.

In some implementations, the matrix phase may be magnetostrictive.

After performing the electro-infiltrating process, the molds (110)—ifused—may be removed and additional processes performed. The result ofelectro-infiltrating the porous microstructure 115 of a nanomaterialinclusion phase with a metal matrix 125 is a two-phase nanocomposite 130as shown in FIG. 1C. The nanomaterials, or inclusion phase, may have afill fraction (volume ratio) in the magnetic matrix in a range of 20-65%by volume. In some embodiments, the volume ratio for the nanomaterial is20-40% by volume, 40-60% by volume, 60-80% by volume, or 80-95% byvolume.

In certain implementations, the thickness of the two-phase composite 130can be any of the following values, about any of the following values,at least any of the following values, at most any of the followingvalues, or within any range having any of the following values asendpoints, though embodiments are not limited thereto: 100 nm, 250 nm,500 nm, 1 μm, 2.5 μm, 5 μm, 25 μm, 50 μm, 100 μm, 250 μm, or 500 μm. Insome cases, the two-phase composite 130 is formed to a thickness betweenabout 100 nm and about 5 μm. In some cases, the two-phase composite 130is formed to a thickness between about 5μm to about 50 μm. In somecases, the two-phase composite 130 is formed to a thickness betweenabout 50 μm and 500 μm.

FIGS. 2A-2D illustrate nanocomposite structures according to someimplementations of the invention. Referring to FIG. 2A, inclusion phasenanomaterial 210 having spherical shapes may be included in a matrix212. Referring to FIG. 2B, inclusion phase core/shell nanomaterialformed of a magnetic nanomaterial 220 having a shell 222 that may beformed of a dielectric can be included in a matrix 224.

This shell 222, which may be a surface oxide layer, affects thematerial's ferromagnetic resonance as well as the overall electricalconductivity of the nanocomposite material. When the magneticnanomaterial is formed of magnetic metal alloy, the ferromagneticresonance properties of the nanomaterial can be controlled, in someembodiments, through controlling the thickness of the dielectric (e.g.,oxide) coating that forms the shell 222 of the of the magnetic metalalloy nanomaterial. Magnetic metal alloy nanomaterial havingcontrollable oxide shell thicknesses can be used in fabricatingnanocomposite magnetic materials for devices, such as microinductors,for high-frequency applications. For example, a dielectric coating maybe formed on Fe—Co alloy nanoparticles by reacting the surface withcorresponding metal oxide precursors, resulting in an amorphous oxidecoated shell. For some implementations using magnetic metal alloynanomaterial having controllable oxide shell thicknesses, the oxideshell may be formed to thicknesses including, but not limited to about0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20 (all values in nm), for examplebetween 1 nm to 10 nm, inclusive.

Referring to FIG. 2C, nanowires 230 can be included in a matrix 232.Referring to FIG. 2D, the nanowires can be aligned nanowires 240 in amatrix 242.

As illustrated in FIGS. 2A-2D, the nanocomposite magnetic material caninclude a matrix phase and an inclusion phase. The matrix phase acts asa binder for the inclusion phase and can include magnetic material.

The nanocomposite magnetic materials can be formed of nanomaterials thatare synthesized with tailored size, shape, magnetic properties, andsurface chemistries. The synthesized materials of the inclusion phasemay be magnetic nanomaterials (providing a. conductively disruptivemagnetic phase) that can then be consolidated into porousmicrostructures via a directed assembly method. The porousmicrostructures can be infiltrated with electroplated ferromagneticmetals to form multi-phase (or “nanocomposite”) magnetic materials.

With reference to FIGS. 2A and 2B, the magnetic nanomaterial may be in ashape of a nanoparticle with diameters of, for example, any of thefollowing values, about any of the following values, at least any of thefollowing values, at most any of the following values, or within anyrange having any of the following values as endpoints, thoughembodiments are not limited thereto (all numerical values are innanometers): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50, 100,150, 200, 250, 300, 350, 400, 410, 420, 430, 440, 450, 460, 470, 480,490, or 500. For example, the nanoparticle diameters can be in a rangeof 1-10 nm, 5-50 nm, 10-50 nm, 50-100 nm, or 100-500 nm. In some cases,all nanoparticles are of a diameter within 10% of each other. In somecases, the nanoparticle diameters used for forming a nanocompositematerial are within any of the ranges.

The magnetic nanomaterial may be in a shape of a nanoflake or nanodiscwith thicknesses of, for example, any of the following values, about anyof the following values, at least any of the following values, at mostany of the following values, or within any range having any of thefollowing values as endpoints, though embodiments are not limitedthereto (all numerical values are in nanometers): 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, or 100. The nanoflakesor nanodiscs may have a diameter of, for example, any of the followingvalues, about any of the following values, at least any of the followingvalues, at most any of the following values, or within any range havingany of the following values as endpoints, though embodiments are notlimited thereto (all numerical values are in nanometers): 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50, 100, 150, 200, 250, 300, 350,400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 550, 600, 650,700, 750, 800, 850, 900, 950, 1000, 1500, 2000, 3000, 4000, 5000.

For example, the thicknesses can be in a range of: 1-10 nm; 10-50 nm; or50-100 nm; and the diameters may be in a range of: 10-50 nm; 50-100 nm;100-500 nm; 500-1000 nm; or 1000-5000 nm. In some cases, the nanoflakesor nanodiscs of a particular material are of a thickness within 10% ofeach other and/or diameter within 10% of each other. In some cases, thenanoflake or nanodisc thicknesses and/or diameters used for forming ananocomposite material are within any of the ranges.

With reference to FIGS. 2C and 2D, the magnetic nanomaterial may be in ashape of a nanorod or nanowire with diameters of, for example, any ofthe following values, about any of the following values, at least any ofthe following values, at most any of the following values, or within anyrange having any of the following values as endpoints, thoughembodiments are not limited thereto (all numerical values are innanometers): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50, 100,150, 200, 250, 300, 350, 400, 410, 420, 430, 440, 450, 460, 470, 480,490, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000. Forexample, the nanorod or nanowire diameters can be in a range of: 10-50nm, 50-100 nm, 100-500 nm, or 500-1000 nm. In some cases, the nanorodsor nanowires are of a diameter within 10% of each other. In some cases,the nanorods or nanowire diameters used for forming a nanocompositematerial are within any of the ranges.

The nanorods or nanowires may have a length of, for example, any of thefollowing values, about any of the following values, at least any of thefollowing values, at most any of the following values, or within anyrange having any of the following values as endpoints, thoughembodiments are not limited thereto (all numerical values are innanometers): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50, 100,150, 200, 250, 300, 350, 400, 410, 420, 430, 440, 450, 460, 470, 480,490, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1500, 2000,3000, 4000, 5000, 6000, 7000, 8000, 9000, 10⁴, or 10⁵. For example, thenanorod or nanowire lengths can be in a range of: 50 -100 nm, 100-500nm, 500-1000 nm, 1-5 μm, 5-10 μm, or 10-50 μm. In some cases, thenanorods or nanowires are of a length within 10% of each other. In somecases, the nanorod or nanowire lengths used for forming a nanocompositematerial are within any of the ranges. It can be appreciated that theterms “nanorod” and “nanowire” refer to a same shape and may be usedinterchangeably as a matter of preference.

In some implementations, the magnetic nanomaterial of the inclusionphase may be provided as a fiber mesh. A fiber mesh can be in the formof a random mesh or an aligned mesh, either configuration fabricated byelectrospinning. The fiber mesh can be formed of metal oxide (e.g.,synthesized magnetic metal oxide), polymer or a polymer composite (apolymer with another material embedded).

Thus, the magnetic nanomaterials for the inclusion phase of thenanocomposite material can be formed in a range of sizes and shapes,including spherical, prismadic, and cubic. Example shapes includenanoparticle, nanoflake, nanodisc, nanorod, and fiber mesh.

For an isolated magnetic nanomaterial, permeability and coercivity ofthe nanomaterials are strongly related to the particle size. Below acertain size, the material will exhibit superparamagnetic behavior, withzero coercivity and higher-than-bulk permeability. Above thissuperparamagnetic limit, the particle exhibits either single-domain ormulti-domain magnetic behavior, with size-dependent magnetic properties.In other words, controlling the size of a particle can have a dramaticeffect on magnetic properties of the particle.

As shown in FIG. 3, below a certain particle size (typically 3-20 nm),the particles may exhibit superparamagnetic behavior, with zerocoercivity. Above this superparamagnetic size, the particles may existin either a single-domain or multi-domain regime, with size-dependentmagnetic properties.

FIGS. 4A-4E illustrate packing arrangements of particles that may beimplemented based on particle size and shape. FIG. 4A depictsclose-packed nanoparticles of spherical particles having similar sizeand shape. A close-packed configuration may be arranged using anexternal magnetic field. FIG. 4B depicts random close-packing ofmonodisperse spherical particles. FIG. 4C illustrates the use of cubicnanoparticles of ferrites fabricated with narrow size distribution,enabling a higher fill fraction as compared to close-packing ofspherical particles. Heterogeneous mixtures of nanomaterial withdiffering sizes may increase fill fraction. Smaller particles—eitherspherical as shown in FIG. 4D or prism-shaped as shown in FIG. 4E can besize-selected to fill the voids between the larger particles and enhancethe total density.

For nanomaterial embedded in a magnetic matrix, an inter-phase magneticexchange coupling phenomenon may occur between particles and atinterfaces between two magnetic material phases. Exchange coupling is aquantum mechanical effect, wherein the magnetic moment of one atom tendsto align the magnetic moment of a neighboring atom, giving rise toferromagnetic behavior. A magnetic material possesses a characteristicexchange length L_(ex) which represents the minimum scale over which themagnetization can vary appreciably. For Co-based alloys, the exchangelength is about 5-10 nm and for Fe-based alloys, the exchange length isabout 20-40 nm.

Thus, for closely packed particles, inter-particle exchange coupling cansignificantly change the net material behavior. In particular, when theparticle size D is scaled down to the exchange length scale, exchangecoupling will dominate over magnetocrystalline anisotropy or othertraditionally dominant magnetic effects. In this regime, the coercivityscales radically as H_(c)∝D⁶, and the permeability as μ_(r)∝1/D⁶.

Therefore, denser packing of the particles increases not only themagnetization, but also reduces the coercivity due to inter-particleexchange coupling. For example, 20 nm Fe₁₀Co₉₀ precursor nanoparticlesexhibited a coercivity of 150 Oe (12 kA/m), but after a plasma pressurecompaction, the coercivity dropped by 30× to only 5 Oe (˜400 A/m).High-frequency inductor applications are benefited by low coercivity inthe magnetic nanomaterials. The particle size can therefore beconsidered and selected based on the exchange length so that thematerial acts as a fully interacting composite instead of a simplemixture of two phases.

The magnetic properties of the nanocomposite magnetic materials can benano-engineered by tailoring sizes of individual nanoparticles,controlling packing density of the two-phase nanocomposite, andinclusion of nanoparticles in a ferromagnetic matrix.

In addition to different sizes and shapes, surface chemistry (includingparticle surface charge, i.e., zeta potential) of the nanoparticles maybe varied to control assembly and packing efficiency (e.g., for particleconsolidation). The nanoparticles with different surface coatings suchas hydrophilic, hydrophobic, anionic, cationic are synthesized. For someof these surface coatings, environmental factors, for example,nonsolvents, salts, external fields, influence the stability of theparticles in a colloidal suspension. External cues can then be used totrigger precipitation and consolidation. In the case of a hydrophilicpolymer coating, a nonpolar solvent could be used to destabilize theparticle dispersion allowing the precipitation of the particles. Thezeta potential can be varied by the surface functionalization during theparticle synthesis or by tuning the solvent properties such as pH andionic strength.

The packing of magnetic particles can be further controlled when thesedestabilizing efforts are performed in the presence of an externalmagnetic field. In a colloidal suspension of magnetic nanoparticles, anexternal magnetic field can affect particle stability. A strong magneticfield can destabilize the particles, causing them to fall out ofsuspension. With modified field patterns, the kinetics of assembly maybe varied and an optimum field strength for maximum packing is obtained.

Additionally, because the particles are magnetic, external magneticfields can be used to beneficially assist the consolidation. Simpleuniform magnetic fields can induce anisotropy, creating texturedcompacts with high permeability and low loss in a preferred easy axis.In addition, the magnetic particles can be assembled into close-packedsuperlattices in the presence of a magnetic field.

As mentioned with respect to FIG. 1A, magnetophoretic assembly usingmagnetic field gradients can be performed to attract the magneticnanomaterial together (and in some cases into the molds). In oneimplementation, magnets can be placed behind the substrate, and lateralagitation of these assembly magnets can help confine the nanomaterialinto the molds. In implementations using nanowire-shaped nanomaterial, auniform magnetic field may be used to align the nanowires to enableanisotropic composites, for example as shown in FIG. 5D.

Electrostatic forces can also be used to assist the nanoparticleconsolidation. For example, particles can be prepared with anionic andcationic surface functionalization. When mixed, Coulombic attractionbetween the positively and negatively charged particles leads to theirprecipitation and consolidation. If the Coulombic attraction is notsufficient to lead to consolidation, salts can be added to the solutionto promote precipitation.

Once the nanocomposite structures are fabricated, RF/microwave and powerconverter devices and systems may be fabricated using planar-substratemanufacturing methods. Magnetic devices such as transformers andinductors can be fabricated from the structured nanocomposite magneticmaterials, for example through silicon microfabrication techniquesand/or printed-circuit board processes to form suitably sized coils. Asubstrate, such as a silicon substrate, may be etched and thenanocomposite materials deposited into the trenches forming the magneticstructures. The described electro-infiltration process can be insertedas a unit-process within a more complex microelectronic fabricationand/or PCB manufacturing process.

According to certain implementations, all of the steps of theelectro-infiltration process can be performed at low-temperature (e.g.,less than 80° C.).

In certain implementations, the electro-infiltration process canfacilitate integration of high-performance magnetic materials withtraditional semiconductor and PCB fabrication platforms. Theelectro-infiltration process can be used to embed a wide variety ofnanomaterials within a metal matrix for realization of a broad array ofmaterials, devices, and systems. In certain implementation, thenanocomposite materials can be integrated with semiconductor devices.Semiconductor devices, with which the nanocomposite materials can beintegrated, include, but are not limited to, transitors, integratedcircuits, optoelectronics, microelectromechanical systems (MEMS),sensors, actuators, or energy converters.

FIGS. 5A and 5B show example air-core inductor and transformerconfigurations that may be fabricated on planar substrates and formed ofthe nanocomposite materials. FIG. 5A is an image of a multi-layer,multi-turn electroplated inductor; and FIG. 5B is an image of amulti-layer, multi-turn electroplated transformer. These images areintended to illustrate device configuration that may be available whenfabricating a device or system with nanocomposite materials as describedherein. Architectures such as multi-turn, spiral coils can be fabricatedwith central cores, half-slab cores, or complete cores. In addition,solenoid or toroidal architectures may also be fabricated.

The power inductors can be designed and fabricated for power systems ina range of 1-1000 W. Advantageous performance enhancement is achieved byuse of magnetic nanocomposite materials, particularly fornext-generation power magnetic devices operating in a switchingfrequency range of 1-500 MHz.

FIG. 5C shows a schematic of a magnetically tunable phase shifter thatmay be fabricated on planar substrates and formed of the nanocompositematerials described herein. The magnetically tunable phase shifter issuitable for phase control of an array antenna. To form the phaseshifter, a coplanar waveguide can be fabricated in an RF circuit board,and then coated with a thin dielectric isolation layer such as epoxy orparylene. A nanocomposite magnetic patch is then integrated on the topsurface of the waveguide. For tunability, the phase shifter device maybe placed between a pair of Helmholtz coils or a pair of permanentmagnets, to establish a transverse, in-plane magnetic field. By biasingwith different magnetic fields, the nanocomposite will exhibit differenteffective magnetic permeability, which alters the wave speed along thewaveguide, resulting in a phase change. A fabricated prototype showed arelative permeability of 1, 10, and 100 (tuned by the bias magnets) andsimulated phase angle changes were 35°, 40°, and 48°, respectively. Sucha device can perform in the low-GHz frequency range.

Using these nanocomposite materials, transformative magneticperformance, such as high saturation and low core loss, are achieved bya highly manufacturable process. For example, soft magnetic cores with aunique combination of magnetic properties such as saturationmagnetization B_(s)>0.8 T, lore loss H_(e)<250 A/m, permeabilityμ_(r)>50, and resistivity ρ>0.1 Ω·m, may be formed.

Transformative hard magnetic properties, such as high saturation andhigh coercivity, can also be achieved by creating exchange springpermanent magnets, where the nanomaterial inclusion phase is a hardmagnetic material, and the matrix or binder is a soft magnetic material.For example, permanent magnets with remanence Br>1.2 T, intrinsiccoercivity H_(ci)>800 kA/m, and maximum energy product >400 kJ/m³, maybe formed.

A greater understanding of the present invention and of its manyadvantages may be had from the following examples, given by way ofillustration. The following examples are illustrative of some of themethods, applications, embodiments and variants of the presentinvention. They are, of course, not to be considered in any waylimitative of the invention. Numerous changes and modifications can bemade with respect to the invention.

Example 1 Fabrication of Soft Magnetic Nanocomposite Materials

For the example demonstration, 30 nm maghemite (γ-Fe₂O₃) particles(inclusion phase) were evaporatively consolidated into photoresist moldson a silicon substrate, and then electro-infiltrated by a lowcoercivity, high saturation Fe—Co alloy (matrix phase) to illustratefabrication of soft magnetic nanocomposite materials up to about 10 μmthick.

The non-conductive iron oxide particles inhibit formation of eddycurrents that could be caused by a uniform Fe—Co alloy.

To form the nanocomposite material materials, silicon substrates weresputtered with a Ti/Cu seed layer (e.g., of about 100 nm). Then,photoresist patterns were formed on the surface to form photoresistmolds. The nanoparticles (γ-Fe₂O₃ particles) were dispersed intodeionized water and then dispensed into the molds, followed byevaporation to consolidate the particles into the molds. This processprovided sufficient particle stability via van der Waals attractionforces for electroplating with the Fe—Co alloy. The Fe—Co alloy waselectroplated up from the bottom surface via constant-current plating,and then the photoresist molds were removed using acetone.

In more detail for the example demonstration, maghemite (γ-Fe₂O₃)nanoparticles with a nominal diameter of 30 nm were used as theinclusion phase, and a low-coercivity, high-saturation Fe—Co alloy wasused as the electro-infiltrated matrix phase. A (100) silicon wafer wassputtered with a 20-nm-thick adhesion layer of Ti and a 100-nm-thickseed layer of Cu. Then AZ 9260 (Shipley) photoresist molds with athickness of 11.5 μm were patterned into various shapes and sizes on thesurface using standard photolithographic techniques.

The 30-nm-diameter γ-Fe₂O₃ nanoparticles (Aldrich-Sigma #544884) weredispersed into deionized (DI) water and then manually dispensed viapipette onto the substrate, followed by evaporation to consolidate theparticles into the molds. The water was evaporated either at roomtemperature for ˜1 hr or by mild heating at 60-70° C. for severalminutes. This process provides sufficient particle stability/bonding forthe subsequent infiltration step. The substrate was next dipped intoisopropanol in order to “wet” the nanoparticles and then soaked in DIwater to displace the isopropanol before the electroplating process.

The Fe—Co alloy was electroplated up from the Ti/Cu seed layer viaconstant-current plating with the current density set as 5-20 mA/cm².Finally the photoresist molds were stripped in acetone, and the sampleswere cleaned with isopropanol and then placed into DI water in asonication bath to remove any excess, unbound nanoparticles on thesurface.

FIGS. 6A and 6B respectively show images of the surface of a samplebefore and after the electro-infiltration step. Some cracks are noted inthe consolidated particle layer, whereas the infiltrated nanocompositeexhibits a fairly uniform surface morphology. For later calculation ofmagnetization and permeability, the sample volume is determined from thesample area and the average layer thickness, measured by both microscopyand profilometry. It is worth noting that the superparamagnetic limitfor maghemite nanoparticles is about 30 nm, which contributes to themagnetic linkages that keep the particles bound in place. For othermaterials and particle sizes, additional steps, such as lowertemperature (˜200° C.) sintering or the use of a magneticback-electrode, may be included to ensure that the consolidatednanoparticle templates remain in place.

FIG. 7 is a SEM image of a cleaved sample cross-section of ananocomposite showing the progression of the electroplating growth frontmoving up through the nanoparticles. As can be seen from FIG. 7 (andverified using EDS elemental mapping), Fe—Co metal grows up from thesubstrate surface and encapsulates the Fe₂O₃ nanoparticles in theelectroplating growth front, as opposed to heaving or displacing theparticles out of the way.

FIG. 8 is a TEM image of a sample cross-section showing a densecomposite with intimate phase boundaries (inset). The cross-sectionshown in FIG. 8 indicates a dense composite, with no apparent pores inthe 2-μm-thick, electro-infiltrated layer. The inset shows an intimatephase boundary between a single Fe₂O₃ particle and the surrounding Fe—Comatrix.

Experiments were conducted for three test structures. In particular, avibrating sample magnetometer (VSM) (ADE Technologies, Model EV9) wasused to measure the in-plane magnetization loops (along the long axis)of three different rectangular (12 mm×5 mm) test structures: anelectroplated Fe—Co thin film (7.5 μm thick), a consolidated γ-Fe₂O₃nanoparticle layer (7.0 μm) without electro-infiltration, and anelectro-infiltrated γ-Fe₂O₃/Fe—Co nanocomposite (1.7 μm). Additionally a“double layer” sample was fabricated. The double layer was formed as alayer of consolidated γ-Fe₂O₃ nanoparticles (16 μm) on top of a layer ofelectroplated Fe—Co (0.4 μm), wherein the saturated magnetic moments ofeach layer are of similar magnitude.

FIG. 9 shows a plot of hysteresis loops of electroplated Fe—Co layer,γ-Fe₂O₃ nanoparticle layer, and γ-Fe₂O₃/Fe—Co nanocomposite layer. FIGS.10A and 10B show schematic representations of a γ-Fe₂O₃/Fe—Conanocomposite layer and a γ-Fe₂O₃/Fe—Co double layer, respectively. FIG.11 shows a comparison of normalized hysteresis loops of γ-Fe₂O₃/Fe—Conanocomposite and double layer. The arrow indicates a kink on the doublelayer curve.

Referring to FIG. 9, the γ-Fe₂O₃/Fe—Co nanocomposite exhibits asaturation of 1.0 T, half that of the Fe—Co (2.0 T). This saturationvalue is much higher than a bulk ferrite (0.3-0.45 T) and on par withpermalloy (˜1.0 T). In addition, the coercivity of the γ-Fe₂O₃/Fe—Conanocomposite is 1.5 kA/m, which is an order of magnitude lower than theγ-Fe₂O₃ nanoparticles (14.0 kA/m) but larger than the Fe—Co (0.3 kA/m).The relative permeabilities of the Fe—Co, γ-Fe₂O₃/Fe—Co composite, andγ-Fe₂O₃/Fe—Co consolidated particles are ˜600, ˜300, and ˜4,respectively. Additionally, the volumetric fraction of the consolidatednanoparticles is estimated to be 40%, based on the ratio of the samplesaturation (0.16 T) and the material saturation (separately measured tobe 0.40 T).

Referring to FIG. 11, the double layer curve can be conceptualized asthe superposition of the individual loops of the γ-Fe₂O₃ nanoparticlesand the Fe—Co metal. A kink is observed on the double layer curve,indicated by the arrow in the figure, indicative of a mixed, two-phasemagnetic response. In contrast, the nanocomposite exhibits a smooth,kink-free curve. These measurements indicate exchange coupling betweenthe nanoparticle inclusion phase and electroplated matrix phase.

The complex permeabilities, given as μ_(r)(ω)=μ′_(r)(ω)−jμ″_(r)(ω), ofthe three rectangular samples were characterized at RF frequencies usinga microstrip line permeameter test fixture and a vector network analyzer(Agilent E5071C). The reflection coefficient was measured with andwithout loading the samples, and the permeability was calculated basedon perturbation method. FIGS. 12A and 12B show plots of the complexrelative permeability for the γ-Fe₂O₃ nanoparticle layer, γ-Fe₂O₃/Fe—Conanocomposite layer and Fe—Co layer, where FIG. 12A shows the real partμ′_(r)(ω) and FIG. 12B shows the imaginary part μ″_(r)(ω).

In FIGS. 12A and 12B, the data is scaled such that the low-frequencypermeability of the Fe—Co matches the DC permeability extracted fromhysteresis loop (600). As illustrated in the Figures, below 100 MHz, thepermeability of the nanocomposite is about half the value of Fe—Coalloy, and an order of magnitude higher than the γ-Fe₂O₃ particles. TheFe—Co alloy has the lowest resonant frequency at about 100 MHz, whilethe frequency for the γ-Fe₂O₃ nanoparticles is higher than 2 GHz. Thenanocomposite exhibits a resonant frequency in between, at about 500MHz, which can be attributed to exchange coupling between the γ-Fe₂O₃nanoparticles and Fe—Co matrix as well as suppression of eddy currentsby the electrically insulating maghemite nanoparticles. The product ofthe low-frequency permeability and resonant frequency can be used as afigure of merit for performance. This product in the nanocomposite isfive times larger than that in the Fe—Co alloy, as indicated by the graylines in the permeability curves. Additionally, because both phases aremagnetic materials, the entire volume is magnetic, thus avoiding the lowmagnetic fractions associated with polymer-based composites.

Example 2 Synthesis of Magnetic Metal Oxide

This example illustrates synthesis of inclusion phase material in theform of a magnetic metal oxide, particularly Zn substituted ferrites,Ni_(1-x)Zn_(x)Fe₂O₄ and Mn_(1-x)Zn_(x)Fe₂O₄.

In some cases, aqueous co-precipitation processes may be used tosynthesize these particles. In other cases, thermal decompositionreactions are used. Polyol and hydro-thermal processes may also be usedin some cases. In yet other cases, solvothermal processes may beutilized.

FIGS. 13A-13C show results of Ni_(0.5)Zn_(0.5)Fe₂O₄ nanoparticlessynthesized using co-precipitation of metal salts in an alkalineenvironment. As illustrated in FIGS. 13A-13C, the particles arerelatively monodisperse with an average diameter of 8-10 nm. One of themany advantages of this method is that it is high yield, making itsuitable for commercial applications.

The surfaces of the ferrite particles can be modified via silanechemistry as shown in FIG. 14. Silanes may be used based on the abilityof silica to form strong covalent bonds with ferrite nanoparticles.Here, a polyethylene oxide (PEO) functionalized silane is grafted to thesurface of the ferrite nanoparticle generating a hydrophilic surfacecoating. By varying the lengths of the PEO and hydrocarbon chains, aparticle that disperses in either polar or nonpolar solvents can beformed.

As another example (not shown in the drawings), the ferritenanoparticles can be synthesized by thermally decomposing metal organicprecursors. Then, a ligand exchange on the synthesized ferritenanoparticles can be performed to allow water solubility andfunctionalization of the ferrite nanoparticles.

Thermal decomposition of metal organic precursors in high temperaturesolvents (e.g., those with higher boiling points) in the presence ofsurfactants can be used to control size and shape, for exampleincreasing resultant particle size.

By varying temperature, heating rate and pressure of synthesisreactions, types of precursors, and types of surfactants, size and shapeof the nanoparticles are optimally controlled. Methods for the size andshape control of Ni_(1-x)Zn_(x)Fe₂O₄ and Mn_(1-x)Zn_(x)Fe₂O₄nanoparticles are discussed below.

For example, iron (III) acetylacetonate (Fe(acac)₃), nickel (II)acetylacetonate (Ni(acac)₂), and zinc (II) acetylacetonate (Zn(acac)₂)can be prepared in stoichiometric amounts and mixed in a hightemperature solvent, such as octadecane or benzyl ether. Alternatively,iron (III) acetylacetonate (Fe(acac)₃), manganese (II) acetylacetonate(Mn(acac)₂), and zinc (II) acetylacetonate (Zn(acac)₂) are mixed instoichiometric amounts in a high temperature solvent, such as octadecaneor benzyl ether. The metal organic precursors may also be mixed withvarying ratios of surfactants such as oleic acid, olylamine, andtri-n-octylphosphine oxide (TOPO), in order to obtain nanoparticles ofspherical, prismadic, or cubic shapes.

The as-synthesized nanoparticles may have a hydrophobic surface coating.Ligand exchange can be performed to stabilize the as-synthesizednanoparticles to allow water solubility as well as subsequentfunctionalization. Ligand exchange can be performed using solutions suchas dimercaptosuccinic acid (DMSA) or thiomalic acid (TMA). These ligandsboth have thiol and carboxylic acid functionalities, which are effectivefor oleic acid coated magnetic particles

The carboxylic acid and thiol functionality can be used for furtherfunctionalization through reactions with the exposed carboxylic acidgroups or thiols. According to certain embodiments, the nanoparticlesmay be synthesized with hydrophilic, hydrophobic, cationic, and anionicligands. This variety in surface functionality can be exploited whenconsolidating the nanoparticles into materials to obtain particleconsolidations with high particle fill factors.

Example 3 Synthesis of Magnetic Metal Alloy Particles

This example illustrates synthesis of inclusion phase material in theform of a magnetic metal alloy. In this example, high magneticsaturation metal alloys such as iron (Fe) and cobalt (Co) alloys aresynthesized and stabilized. Fe_(100-x)Co_(x) alloy nanoparticles exhibithigh magnetic moment and low coercivity, and the highest saturationmagnetization of 2.4 T among all ferromagnetic materials.

As an illustrative example, body-centered cubic (bcc) nanoparticlescomprising soft magnetic Fe_(100-x)Co_(x), where x=35 to 40, with sizesin a range from 5 to 50 nm have been synthesized. The magneticproperties of the Fe—Co nanoparticles are optimized by varyingcompositions and particle sizes of the metal alloy nanoparticles.Moreover, the nanoparticles are functionalized with various surfaceagents such as polyvinylpyrrolidone to inhibit particle oxidation andagglomeration, while preserving soft magnetic properties to be close tobulk values.

For particles sizes in a range of 25-50 nm, a modified polyol process isused for synthesizing metal alloy nanoparticles. The modified polyolprocess comprises generating supersaturation, nucleation, and subsequentgrowing of the nanoparticles. The modified polyol process uses solventacting as a reducing and oxidation-preventing agent in addition to themolecular or atomic level control and process parameters are varied tocontrol and modify the process. For example, nanoparticle sizes andcompositions can be altered by controlling reaction parameters, such asreaction temperature and concentration of metal precursors.

Fe(II) chloride and cobalt acetate tetrahydrate is dissolved in ethyleneglycol with appropriate amounts of NaOH. Polyvinylpyrrolidone (PVP) isadded as a surfactant to protect the particles from surface oxidation.Under an inert atmosphere, the solution is heated to 120° C. withconstant mechanical stirring, and refluxed for a maximum period of onehour. The suspension is then cooled, and the black precipitatedparticles are separated via centrifuging, followed triple rinsing inethanol.

For some intended high-frequency applications such as microinductors,the thickness of the oxide coating is controlled in order to control theferromagnetic resonance properties. Hence, an additional method isperformed to prepare amorphous oxide shell coated Fe—Co alloynanoparticles using a two-step polyol process.

During the first step, the Fe—Co alloy nanoparticles are prepared usingthe above method. As part of the second step, dielectric coatings areformed by reacting the nanoparticles with corresponding metal oxideprecursors at surfaces. For example, tetraethyl orthosilicate, aluminumisopropoxide, and zirconium (iv) acetyl acetonate are used to makeamorphous SiO₂, Al₂O₃, and ZrO₂ coatings, respectively.

For smaller Fe—Co particles in a range of 5-20 nm, an alternativeapproach can be used employing thermal co-decomposition of iron andcobalt acetylacetonate metal precursors in benzyl ether solvents oroctyl ether solvents. The stabilization can be achieved by passivatingthe polymers or ligands during the thermal co-decomposition synthesisreactions. For example, the synthesis is implemented in a reductivedecomposition of Fe(III) acetylacetonate (Fe(acac)₃) and Co(II)acetylacetonate (Co(acac)₂) in a mixture of surfactants and1,2-hexadecanediol under a gas mixture of 93% Ar+7% H₂ at 300° C. Sizesof the synthesized nanoparticles are controlled by varying the bindingligands. For example, particles of sizes of about 20 nm are formed whena mixture of oleic acid and oleyl amine is used as surfactants.Conversely, particles of sizes of about 10 nm are obtained by using acombination of oleic acid and trioctylphosphine (TOP) as surfactants.The particles are made air-stable with enhanced magnetic properties byannealing at modest temperatures.

Certain aspects of the invention provide the following non-limitingembodiments:

Example 1. A nanocomposite magnetic material, comprising: a magneticmetal matrix phase; and an inclusion phase of consolidated nanomaterialsbound by the magnetic metal matrix phase.

Example 2. The nanocomposite magnetic material of example 1, wherein themagnetic metal matrix phase comprises a soft magnetic material.

Example 3. The nanocomposite magnetic material of example 2, wherein thesoft magnetic material comprises Ni, Fe, Co, Ni—Fe alloy, or Co—Fealloy.

Example 4. The nanocomposite magnetic material of example 1, wherein themagnetic metal matrix phase comprises a hard magnetic material.

Example 5. The nanocomposite magnetic material of example 4, wherein thehard magnetic material comprises alloys of Co—Ni, Co—Pt, Fe—Pt, Nd—Fe—B,or Sm—Co.

Example 6. The nanocomposite magnetic material of example 1, wherein themagnetic metal matrix phase comprises a magnetostrictive material.

Example 7. The nanocomposite magnetic material of any of exampleswherein the inclusion phase comprises ceramic particles or polymernanomaterials.

Example 8. The nanocomposite magnetic material of any of exampleswherein the inclusion phase comprises Ni_(1-x)Zn_(x)Fe₂O₄ orMn_(1-x)Zn_(x)Fe₂O₄, where 0≦x≦1.

Example 9. The nanocomposite magnetic material of any of examples 1-6,wherein the inclusion phase comprises nanomaterials of a metal alloywith a dielectric shell.

Example 10. The nanocomposite magnetic material of any of examples 1-9,wherein the inclusion phase has a fill fraction of 20-40% by volume.

Example 11. The nanocomposite magnetic material of any of examples 1-9,wherein the inclusion phase has a fill fraction of 40-60% by volume.

Example 12. The nanocomposite magnetic material of any of examples 1-9,wherein the inclusion phase has a fill fraction of 60-80% by volume.

Example 13. The nanocomposite magnetic material of any of examples 1-9,wherein the inclusion phase has a fill fraction of 80-95% by volume.

Example 14. The nanocomposite magnetic material of any of examples 1-13,wherein a thickness of the nanocomposite magnetic material is in a rangeof about 100 nm to about 5 μm.

Example 15. The nanocomposite magnetic material of any of examples 1-13,wherein a thickness of the nanocomposite magnetic material is in a rangeof about 50 μm to about 500 μm.

Example 16. The nanocomposite magnetic material of any of examples 1-13,wherein a thickness of the nanocomposite magnetic material is in a rangeof about 100 nm to about 500 μm.

Example 17. A method of forming a nanocomposite magnetic material,comprising: consolidating synthesized nanomaterials of at least oneinclusion phase into a porous microstructure; and performing anelectro-infiltration process to fill voids of the porous microstructurewith a magnetic metal matrix phase.

Example 18. The method of example 17, wherein consolidating synthesizednanomaterials comprises: using at least one magnet or at least oneexternal magnetic field to direct the synthesized particles.

Example 19. The method of example 17, wherein consolidating synthesizednanomaterials comprises: using an applied electric bias to generate anelectric field to direct the synthesized particles.

Example 20. The method of any of examples 17-19, further comprising:selecting the synthesized nanomaterials according to at least one ofsize, shape, surface coating and magnetic properties.

Example 21. The method of example 20, wherein the synthesizednanomaterials comprise at least one shape selected from a groupconsisting of spherical, nanoflake, nanodisc, nanorod, and nanowire.

Example 22. The method of any of examples 17-21, further comprising:forming a mold on a planar substrate, wherein the synthesizednanomaterials are consolidated in the mold; and removing the mold afterperforming the electro-infiltration process leaving bound consolidatednanomaterials on the planar substrate.

Example 23. The method of example 22, further comprising: removing thebound consolidated nanomaterials from the planar substrate.

Example 24. The method of any of examples 17-23, wherein performing theelectro-infiltration process comprises: electroplating the porousmicrostructure with the metal magnetic matrix phase from a bottomsurface to a top surface of the porous microstructure.

Example 25. The method of any of examples 17-23, wherein performing theelectro-infiltration process comprises: electroless plating the porousmicrostructure with the metal magnetic matrix phase.

Example 26. A method comprising: performing semiconductor processing tofabricate at least one semiconductor device on a semiconductor wafer;and forming a structure comprising magnetic material on thesemiconductor wafer using a nanocomposite magnetic material, thenanocomposite magnetic material formed by consolidating synthesizednanomaterials of at least one inclusion phase into a porousmicrostructure; and performing an electro-infiltration process to fillvoids of the porous microstructure with a magnetic metal matrix phase.

Example 27. The method of example 26, wherein consolidating synthesizednanomaterials comprises: using at least one magnet or at least oneexternal magnetic field to direct the synthesized particles.

Example 28. The method of example 26, wherein consolidating synthesizednanomaterials comprises: using an applied electric bias to generate anelectric field to direct the synthesized particles.

Example 29. The method of any of examples 26-28, wherein thenanocomposite magnetic material is further formed by: selecting thesynthesized nanomaterials according to at least one of size, shape,surface coating and magnetic properties.

Example 30. The method of example 29, wherein the synthesizednanomaterials comprise at least one shape selected from a groupconsisting of spherical, nanoflake, nanodisc, nanorod, and nanowire.

Example 31. The method of any of examples 26-30, wherein thenanocomposite magnetic material is further formed by: forming a mold ona planar substrate, wherein the synthesized nanomaterials areconsolidated in the mold; and removing the mold after performing theelectro-infiltration process leaving bound consolidated nanomaterials onthe planar substrate.

Example 32. The method of example 31, wherein the nanocomposite magneticmaterial is further formed by: removing the bound consolidatednanomaterials from the planar substrate.

Example 33. The method of any of examples 26-32, wherein performing theelectro-infiltration process comprises: electroplating the porousmicrostructure with the metal magnetic matrix phase from a bottomsurface to a top surface of the porous microstructure.

Example 34. The method of any of examples 26-32, wherein performing theelectro-infiltration process comprises: electroless plating the porousmicrostructure with the metal magnetic matrix phase.

Example 35. The method of any of examples 26-34, wherein thenanocomposite magnetic material comprises a plurality of boundconsolidated nanomaterials of the at least one inclusion phase and themagnetic metal matrix phase.

Example 36. The method of example 35, wherein the plurality of boundconsolidated nanomaterials are of different sizes and/or shapes.

Example 37. The method of any of examples 35-36, wherein the pluralityof bound consolidated nanomaterials comprise a heterogeneous mix ofbound consolidated nanomaterials in which some of the bound consolidatednanomaterials have different characteristics than other of the boundconsolidated nanomaterials.

Example 38. The method of any of examples 35-37, wherein a thickness ofat least some of the bound consolidated nanomaterials is in a range ofabout 100 nm to about 5 um.

Example 39. The method of any of examples 35-37, wherein a thickness ofat least some of the bound consolidated nanomaterials is in a range ofabout 50 μm to about 500 μm.

Example 40. The method of any of examples 35-37, wherein a thickness ofat least some of the bound consolidated nanomaterials is in a range ofabout 100 nm to about 500 μm.

Example 41. The method of any of examples 26-40, wherein the magneticmetal matrix phase comprises a soft magnetic material.

Example 42. The method of example 41, wherein the soft magnetic materialcomprises Ni, Fe, Co, Ni—Fe alloy, or Co—Fe alloy.

Example 43. The method of any of examples 26-40, wherein the magneticmetal matrix phase comprises a hard magnetic material.

Example 44. The method of example 43, wherein the hard magnetic materialcomprises alloys of Co—Ni, Co—Pt, Fe—Pt, Nd—Fe—B, or Sm—Co.

Example 45. The method of any of examples 26-40, wherein the magneticmetal matrix phase comprises a magnetostrictive material.

Example 46. The method of any of examples 26-45, wherein the at leastone inclusion phase comprises ceramic particles or polymernanomaterials.

Example 47. The method of any of examples 26-45, wherein the at east oneinclusion phase comprises Ni_(1-x)Zn_(x)Fe₂O₄ or Mn_(1-x)Zn_(x)Fe₂O₄,where 0 x 1.

Example 48. The method of any of examples 26-45, wherein the at leastone inclusion phase comprises nanomaterials of a metal alloy with adielectric shell.

Example 49. The method of any of examples 26-48, wherein the at leastone inclusion phase has a fill fraction of 20-40% by volume.

Example 50. The method of any of examples 26-48, wherein the at leastone inclusion phase has a fill fraction of 40-60% by volume.

Example 51. The method of any of examples 26-48, wherein the at east oneinclusion phase has a fill fraction of 60-80% by volume.

Example 52. The method of any of examples 26-48, wherein the at leastone inclusion phase has a fill fraction of 80-95% by volume.

Example 53. The method of any of examples 35-48, wherein the pluralityof bound consolidated nanomaterials comprises: a first plurality ofbound consolidated nanomaterials of a first inclusion phase and a firstmagnetic metal matrix phase; and a second plurality of boundconsolidated nanomaterials of a second inclusion phase and a secondmagnetic metal matrix phase, wherein at least one of the first inclusionphase and the first magnetic metal phase of the first plurality of boundconsolidated nanomaterials is different than the second inclusion phaseand the second magnetic metal phase of the second plurality of boundconsolidated nanomaterials.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. In addition, anyelements or limitations of any invention or embodiment thereof disclosedherein can be combined with any and/or all other elements or limitations(individually or in any combination) or any other invention orembodiment thereof disclosed herein, and all such combinations arecontemplated with the scope of the invention without limitation thereto.

It should be understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication.

All patents, patent applications, provisional applications, andpublications referred to or cited herein are incorporated by referencein their entirety, including all figures and tables, to the extent theyare not inconsistent with the explicit teachings of this specification.

What is claimed is:
 1. A method of forming a nanocomposite magneticmaterial, comprising: consolidating synthesized nanomaterials of atleast one inclusion phase into a porous microstructure; and performingan electro-infiltration process to fill voids of the porousmicrostructure with a magnetic metal matrix phase.
 2. The method ofclaim 1, wherein performing the electro-infiltration process compriseselectroplating the magnetic metal matrix phase within the voids of theporous microstructure.
 3. The method of claim 1, wherein consolidatingsynthesized nanomaterials comprises using at least one magnet or atleast one external magnetic field to direct the synthesized particles.4. The method of claim 1, wherein consolidating synthesizednanomaterials comprises using an applied electric bias to generate anelectric field to direct the synthesized particles.
 5. The method ofclaim 1, further comprising: selecting the synthesized nanomaterialsaccording to at least one of size, shape, surface coating and magneticproperties; forming a mold on a planar substrate, wherein thesynthesized nanomaterials are consolidated in the mold; removing themold after performing the electro-infiltration process leaving boundconsolidated nanomaterials on the planar substrate; and removing thebound consolidated nanomaterials from the planar substrate, wherein thesynthesized nanomaterials comprise at least one shape selected from agroup consisting of spherical, nanoflake, nanodisc, nanorod, andnanowire.
 6. The method of claim 1, wherein performing theelectro-infiltration process comprises electroplating the metal magneticmatrix phase within the voids of the porous microstructure from a bottomsurface to a top surface of the porous microstructure.
 7. The method ofclaim 1, wherein performing the electro-infiltration process compriseselectroless plating of the metal magnetic matrix phase within the voidsof the porous microstructure.
 8. A method comprising: performingsemiconductor processing to fabricate at least one semiconductor deviceon a semiconductor wafer; and forming a structure comprising magneticmaterial on the semiconductor wafer using a nanocomposite magneticmaterial, the nanocomposite magnetic material formed by consolidatingsynthesized nanomaterials of at least one inclusion phase into a porousmicrostructure; and performing an electro-infiltration process to fillvoids of the porous microstructure with a magnetic metal matrix phase,wherein the nanocomposite magnetic material comprises a plurality ofbound consolidated nanomaterials of the at least one inclusion phase andthe magnetic metal matrix phase.
 9. The method of claim 8, whereinperforming the electro-infiltration process comprises electroplating themagnetic metal matrix phase within the voids of the porousmicrostructure.
 10. The method of claim 8, wherein performing theelectro-infiltration process comprises electroplating the metal magneticmatrix phase within the voids of the porous microstructure from a bottomsurface to a top surface of the porous microstructure.
 11. The method ofclaim 8, wherein performing the electro-infiltration process compriseselectroless plating of the metal magnetic matrix phase within the voidsof the porous microstructure.
 12. The method of claim 8, wherein theplurality of bound consolidated nanomaterials are a heterogeneousmixture of different sizes, different shapes, or both.
 13. The method ofclaim 8, wherein the plurality of bound consolidated nanomaterials havea same size and/or shape.
 14. The method of claim 8, wherein theplurality of bound consolidated nanomaterials comprises: a firstplurality of bound consolidated nanomaterials of a first inclusion phaseand a first magnetic metal matrix phase; and a second plurality of boundconsolidated nanomaterials of a second inclusion phase and a secondmagnetic metal matrix phase, wherein at least one of the first inclusionphase and the first magnetic metal phase of the first plurality of boundconsolidated nanomaterials is different than the second inclusion phaseand the second magnetic metal phase of the second plurality of boundconsolidated nanomaterials.